Which of the following organisms is located only in the 3rd trophic level of the soil food web?
2 answers:
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Answer:
Explanation:
An antimicrobial agent is a natural or synthetic chemical that kills or inhibits the growth of microorganisms. Bacteria have a mechanism of transferring genomic material called <em>horizontal gene transfer</em><em>, the movement of genes between cells that are not direct descendants of one another</em>. Horizontal gene transfer allows cells to quickly acquire new characteristics and drives metabolic diversity. <u>One of the characteristics usually acquired is the resistance to antibiotics</u>.
Three mechanisms of genetic exchange are known in prokaryotes:
(1) transformation, in which free DNA released from one cell is taken up by another; (2) transduction, in which DNA transfer is mediated by a virus; and (3) conjugation, in which DNA transfer requires cell-to-cell contact and a conjugative plasmid in the donor cell.
Examples of genes transferred by transducing bacteriophages include multiple antibiotic resistance genes among strains of <em>Salmonella enterica </em>serovar <em>Typhimurium</em>, Shiga-like toxin genes in <em>Escherichia coli</em>, virulence factors in <em>Vibrio cholerae</em>, and genes encoding photosynthetic proteins in cyanobacteria.
Conjugative plasmids use a mechanism to transfer copies of themselves and the genes they encode, such as those for antibiotic resistance, to new host cells.
